Telephone system



April 17, 1934. L, WALLER 1,954,967

TELEPHONE SYSTEM Filed Nov. 10, 1932 FIG. 1

CON.

PRIVATE BRANCH EXUMNGE P.B.E.

E //v l EN TOR L. R. W LLER BY am wmw A TTORNEV Patented Apr. 17, 1934 STATE to Western Electric Company, Incorporated,

New York, N. Y., a corporation of New York Application November 10, 1932, Serial No. 642,050

10 Claims.

This invention relates to telephone systems and particularly to trunk circuits and automatic equipments for use in small private branch exchange systems.

Its object is to improve such circuits and equipments to increase the flexibility and use thereof for different types of connections in the private branch exchanges.

Heretofore systems. have been devised for switching calls incoming to an exchange to subscribers located in said exchange or to trunks outgoing from the exchange. In such automatic systems the dialing is usually done either over the tip and ring conductors by interrupting a connection between these conductors or by a simplex arrangement in which the tip and ring conductors are connected together at the sending and receiving stations and interrupted by the dial pulses.

A feature of the present invention is the provision in a selector, associated with an incoming trunk and by means of which connections may be established through succeeding switches or connectors to local subscribers lines or to trunks leading to other offices terminating in other automatic switches of means for repeating incoming impulses to a special conductor for the control of the connector and for repeating such impulses over the tip and ring conductors in simplex when a trunk has been selected.

The invention has been illustrated in the accompanying drawing in which:

Fig. 1 shows in diagrammatic form a trunk incoming to a private branch exchange terminatingcin a selector embodying the features of this invention, this selector having access to a connector through which a connection may be made to a local subscribers line and having access to trunks leading to a distant oifice where said trunks terminate in switches through which connections may be extended to called subscribers in this office;

While Fig. 2 shows the complete circuit arrangement of the incoming trunk and associated selector, with a local connector and a trunk leading to a distant oflice in less detail.

Referring now to Fig. 2, the trunk circuit 15 incoming from a distant office to the private branch exchange PBE, may be seized in any well known manner for transmission of selecting impulses over the tip and ring conductors in simplex. The first of these impulses'seizes the selector switch 16 by operating the relay 17 over a circuit from battery, lower armature and back contact of relay 18, the two windings of relay 1'? in parallel, the left-hand windings of the repeating coil 19, the tip and ring conductors of trunk 15 through the armatures and back contact of the cut-off relay 20 to a ground at the distant office. Relay 1'7 closes an obvious circuit for the operation of relay 21. Relay 21 closes an obvious circuit for the operation of relay 22 and prepares a holding circuit for several of the relays, and extends the pulsing circuit controlled by relay 17 from the ground at the armature and back contact of relay 17, third lower armature and back contact of relay 23, inner right-hand armature and front contact of relay 22 to the inner righthand armature and back contact of relay 24 through the winding of the stepping magnet 25 to battery. The stepping magnet 25 controls the switch banks 26 and 27 of a ringing code selecting switch.

Referring to the operation of relay 22, this re lay opens a connection at its right-hand armature and back contact from a ground interrupter 29 which is used as hereinbefore described for releasing purposes, opens at its left-hand armature and back contact a circuit for the cut-ofi relay 20 to prevent this relay from operating, andapplies a connection to ground at this armature and its front contact to the sleeve lead of the three leads 31 terminating in connector banks, through which the trunk 15 may be seized for outgoing calls. 7

The ringing code switch selects the proper code signal to be transmitted to a desired party which may be on a party line group or on a single line. The brushes of the banks 26, 27 are operated by the magnet 25 in position to receive the proper code signal. The code signals may be ground connections interrupted in different manners and connected through terminals of bank 27 while the terminals of bank 26 may be connected to ground in groups of five to cause the necessary establishing of circuit connections for the transmission of the codes in the ringing code interrupting device 59 not shown in detail.

On the first release of relay 17 due to the first dial impulse, a circuit is closed for the operation of stepping magnet 25. Relay 32 is also operated in an obvious branch circuit. The arrangement of the ringing switch may be such that brushes of the banks 26, 27 do not move from the first terminal until after the stepping magnet 25 has released. Relay 21 is slow in releasing so that it will remain operated during the pulsing. Relay 32in operating closes obvious circuits for the operation of relays 33 and 34. Relay 33 prepares a busy test circuit as hereinafter described and relay 34 prevents the operation of relays 24 and 36. The subsequent operations and release of pulsing relay 17 causes the magnet 25 to step the brushes of banks 26, 27 to terminals corresponding to the desired code number. At the completion of this series of impulses, relay 17 remains operated and after an interval relays 33 and 34 are released. The release of relay 34 now closes a circuit for the operation of relay 24 from battery through the winding of relay 24, inner left-hand armature and back contact of relay 34 to ground at the off-normal contacts 37 closed by the movement of the ringing code switch off normal. As relay 33 is slow in releasing a circuit was closed momentarily from battery, winding of relay 39, outer right-hand armature and back contact of relay 32, armature and front contact of relay 33, to the S1 lead and its wiper of the selector switch 16. This is a busy test circuit, but as the switch 16 is in normal position no test is made at this time. When relay 24 operated, it closed a locking circuit for itself through its left-hand armature and front contact to the off-normal contacts 37, and transferred the pulsing circuit from the magnet 25 to the stepping magnet 40 for selector 16 at its inner right-hand armature and front contact.

In response to the next digit or series of impulses the selector 16 is stepped to terminals leading to a connector, such as 35, which has access to the group of lines containing the called partys line, if a local call in the private branch exchange is desired. Relays 32, 33, and 34 operate as hereinbefore described, relay 34 new opening the operating circuit of relay 36 so that this relay will not operate until the second digit is completed. On the release of relay 34, when the second digit is completed, relay 36 operates over a circuit from battery, winding of this relay, outer left-hand armature and back contact of relay 34, off-normal contacts 42 of the selector 16 to ground. Relay 36 looks to this ground at its left-hand armature and front contact independent of relay 34. Relay 36 now transfers the pulsing circuit at its inner right-hand armature and front contact to the lead S2 and its wiper of the selector 16 through the middle righthand armature and back contact of relay 43. This lead is then used as the pulsing lead for the operation and control of the connector 35.

The dialing of the third digit will now take place in the same manner as hereinbefore described but with the impulse transmitted over lead S2 to the stepping magnet 45 of the connector 35. As soon as the connector 35 is stepped from its normal position, a ground is fed back over lead S3 from the off-normal contact 47, and the corresponding wiper through the winding of relay 49 to battery to cause the operation of this relay. The purpose of this relay will become apparent as the description proceeds. When the wipers of connector 35 have been advanced to the desired line and this line is busy, a ground will be present on the sleeve terminal and be transmitted back over the sleeve lead S1 and the corresponding wiper to cause the operation of relay 39 over the circuit hereinbefore mentioned on the release of relay 32 and due to the slow release of relay 33. This relay in operating closes an obvious circuit for the operation of relay 43. Relay 43 locks over its inner right-hand armature and front contact to ground at relay 21, and opens the circult at the inner left-hand armature and back contact for the cutting through relay 23. Relay 43 also opens the pulsing circuit at its middle right-hand armature and back contact thus preventing the operation of the connector 35 should the subscriber dial another digit. Relay 43 also closes a circuit to start the busy tone to be transmitted back over'the trunk 15. This tone will be supplied from a source at 51, not shown, through the outer left-hand armature and front contact of relay 43 and the lower right-hand winding of repeating coil 19 through the contacts of relays 52 and 34 through a resistance to battery, and inductive busy tone is thereby transmitted through repeating coil 19 to the trunk 15. If the called line is idle, the usual cut-off relay in the called subscribers line circuit operates through the sleeve circuit over lead S1 on the release of relay 33 to cause the operation of relay 23. This circuit may be traced from ground, windings of relays 52 and 23 in series, inner lefthand armature and back contact of relay 43, armature and back contact of relay 33, over the sleeve lead S1 to the battery through the corresponding wipers of selector 16 and connector 35 and the cut-off relay of the called subscribers line. Relay 52 does not operate in this circuit due to its marginal characteristics. Relay 23 in operating completes the talking path to the called line over the tip and ring conductors at its upper and lower inner armature and front contacts, opens the pulsing circuit at its third lower armature and back contact to prevent further stepping of the connector 35, and prepares circuits for relays 54 and 34 to prepare the ringing code circuit. Relay 54 operates over a circuit from battery, winding of this relay, right-hand armature and back contact of relay 56, make-before-break contact of relay 54, second lower armature and front contact of relay 23, through the brush and contacts of bank 26 to the ground found in the code ringing interrupter circuit associated with a group of five codes including the code dialed. This ground should only be applied when the brushes of the code ringing interrupters are in normal position in order that ringing may start only at the commencement of a code. Relay 54 in operating locks to ground at the relay 21 and leaves the original connection to the brush of bank 26 open to prevent interference with other trunks. Relay 54 also closes a circuit for relay 58 from battery, winding of this relay, left-hand armature and front contact of relay 54, brush of bank 2'7 to the particular terminal on which this brush has stopped in selecting the code. Relay 58 will now follow the interruptions supplied from the code ringing interrupter circuit connected to this terminal and correspondingly places alternating current and ground out over the tip and ring conductors to the called party at the inner upper and lower armatures and front contacts from the source connected at 60. Relay 58 also passes alternating current from the source at 60 over the upper outer armature and front contact and the tip conductor to the calling party to give an indication that the called party code is being rung, When relay 23 operated a circuit was also closed for relay 34 from battery, winding of this relay, lower outer armature and front contact of relay 23, second lower armature and front contact of relay 23, brush of bank 26 to ground. Relay 34, therefore, follows the ground impulses received over this brush when the code interrupter circuits are in normal position. When relay 34 is in normal position, battery through a resistance is connected at the outer left-hand armature and back contact, inner lefthand armature and back contact of relay 62, to the mid-point of the righthand windings of the repeating coil 19 so as to absorb any charges on the line caused by the ringing.

When the called party answers a simplex ground at this partys subset is placed on the line on the next operation of relay 34, a circuit will be closed for the operation of relay 18 from battery, winding of this relay, outer left-hand armature and front contact of relay 34, inner lefthand armature and back contact of relay 62, the mid-point between the right-hand windings of repeating coil 19 out over the tip and ring conductors to this ground. Ringing can, therefore, only be tripped at the end of a code. Relay 18 in operating closes a circuit for the operation of relay 56 from battery, winding of this relay and the upper inner armature and front contact of relay 18 to ground. Relay 18 also removes the shunt around the resistance 63 at its lower armature and back contact, thereby permitting the supervisory relay at the distant end of trunk 15 to release as an indication that the called party has answered. Relay 1'7, however, remains operated in series with the resistance 63. Relay 56 in operating opens the circuit at its right-hand armature and back contact for relay 54 causing its release and is locked at its inner left-hand armature and front contact to ground at relay 21. Relay 54 in releasing opens the circuit for relay 58, thus preventing further ringing out over the line. Relay 58 in releasing completes the talking circuit between the calling and called parties.

When the called party hangs up receiver, relay 18 releases and shunts the resistance 63 and thereby indicates by the operation of the supervisory relay at the distant end that release has taken place. The release of the selector is under the control of an operator or the calling party, release taking place when the trunk 15 is disconnected at the distant end which causes relay 1'? to release and thereby restores the circuit to normal by the release of relays 21 and 22. The relay 22 in releasing now feeds back interrupted ground from the interrupter 29 and. through the armature and front contact of relay 49, outer right-hand armature and front contact of relay 36, inner right-hand armature and front contact of relay 24 and wlnding'of relay 32 to battery. Relay 32 operates causing the operation of relay 34 and remains due to its slow release characteristics operated as long as this interrupted ground connection circuit is maintained. The interrupted ground connection is also fed through the armature and front contact of relay 49 over middle right-hand armature and back contact of relay 43, lead S2, winding of stepping magnet 45 to battery causing the connector 35 to he stepped to normal. When the off-normal contact 47 opens, the circuit for relay 49 is opened to cause this relay to release. When relay 49 releases the interrupted'ground is transmitted over the armature and back contact of relay 43, outer right hand armature and front contact of relay 36 to the stepping magnet 40 of the selector 16 causing this selector to be stepped back to normal. When the normal position has been reached the ground at the off-normal contacts 42 is removed causing the release of relay 36. Interrupter ground is now transmitted over the outer right-hand armature and back contact of relay 36, middle right hand armature and front contact of relay 24, winding of the stepping magnet 25 to battery causing the ringing code switch to be operated until it returns to normal when the ground is removed at the off-normal contact 37 causing the release of relay 24.

It should be understood that if the operator fails to dial the complete number and, for example, if he only dials the first digit, and then abandons the connection, the interrupted ground from 26 will be transmitted to the stepping magnet 25 as hereinbefore described to return the ringing code switch to normal. If he dials two digits and then abandons the call, the stepping magnet 40 is similarly returned to normal.

Should the calling operator desire tomake a connection over a trunk to a distant step by-step ciiice, the operations are similar up to the point whore a trunk such as extending to the distant ofiice is selected by the selector 16.

The first digit sci-acts the desired code and the second digit selects the trunk 65. In this case relays 32, 33 and 34 operate as before. Relay 34 in operating opens the operating circuit for relay 36 so that this relay will not operate until the second digit is completed. On the release of relay 34, when the second digit is completed, relay 36 operates and locks to the off-normal contacts 42 of selector 16. Relay 36 now transfers the pulsing circuit as hereinbefore to the lead S2 through the middle right-hand armature and back contact of relay 43.

If the desired trunk is idle, the usual cut-off relay such as 66 of the selected trunk is connected to battery and this connection now extends over lead S1 through the windings of relays 23 and 62 to ground. The resistance of the circuit is in this case such that both relays 23 and 52 operate When relay 23 operates, it completes a path to the called trunk over the tip and ring conductor and transfers the pulsing circuit through the contacts of relay 62 to the mid-point of the right-hand windings of the repeating coil 19 from ground at the armature and back contact of relay 1'7, third and lower armature and front contact of relay 23, righthand armature and front contact and inner left hand armature and front contact of relay 62 through the windings of repeating coil 19 over the tip and ring conductors to the trunk. As a simplex ground is normally present through the windings of the line relay at the distant ofilce on the tip and ring conductors of the trunk 65 and as the winding of relay 68 is connected to battery and through the contacts of relay 62 for the pulsing circuit connector, relay 68 will now be operated in series with the line relay at the distant end of the trunk. Relay 68 in operating from this simplex ground places a guarding shunt on resistance 63 and causes the operation of re lay 18 over an obvious circuit. Relay 18 in operating looks through its upper outer armature and front contact under the control of relay 62 to ground at relay 21. Relay 56 is also operated by relay 18 and opens the circuit for relay 54 to prevent this relay from operating on the operation of relay 23 and-thus prevent ringing current from being sent out over the trunk at this time. The circuits are now ready for pulsing and as the pulsing or line relay at the distant end of the trunk is held operated through the simplex circuit hereinbefore mentioned, the release of the pulsing relay 17, on the first pulse of the next digit places a shunting ground on this connection and causes the pulsing relay at the distant end to release in response to this impulse.

Relay 68, however, is maintained operated. When the pulsing relay 17 reoperates, the pulsing relay at the distant end of the trunk is reoperated. This pulsing relay at the distant end is caused to operate in unison with relay 1'? to advance the step-by-step switch at this ofiice in accordance with the dialed digit.

When the subscriber in the distant oflice answers the call, a high resistance is cut into the simplex circuit causing relay 68 to release. Relay 68 in releasing removes the shunt around the resistance 63 thus providing supervision back over trunk 15 to indicate that the subscriber at the distant end has answered. Talking may now take place over the connection. When the called subscriber hangs up his receiver at the distant end, the high resistance is removed and relay 68 is again operated to shunt out the resistance 63 to notify the operator at the call originating end of trunk 15 that release has taken place. The operator may then release the connection as hereinbefore described in connection with a local call. If the trunk selected by selector 16 is busy the same kind of busy test is applied as in the case of a local call.

It should be understood that while but a single embodiment of the invention has been shown and described, it may readily be applied to other similar circuits Without departing from the spirit thereof.

What is claimed is:

I. In a telephone system, a selector, connectors and trunk lines selectable by said selector, means for repeating a series of impulses incoming to said selector in one manner to a selected connector, means for controlling the operation of said selected connector by said repeated impulses, and means for repeating a series of impulses in coming to said'selector in another manner to a trunk if selected.

2. In a telephone system, a selector, connectors and trunk lines selectable by said selector, a relay in said selector, means for repeating impulses incoming to the selector over a certain conductor to a selected connector, means for operating said relay in response to the selection of a trunk, and means operative after the operation of said relay for repeating impulses incoming to said selector over the selected trunk.

3. In a telephone system, a selector, connectors and trunk lines selectable by said selector, a relay in said selector, means for repeating impulses incoming to the selector over a certain conductor to a selected connector, means for operating said relay in response to the selection of a trunk, and means operative after the operation of said relay, for repeating impulses incoming to the selector over the tip and ring conductors of the selected trunk in simplex.

4. In a telephone system, a switch, two different kinds of connections selectable by said switch,

means for repeating impulses incoming to the switch to a selected connection over one conductor thereof in response to the selection of one kind of connection and over two conductors thereof in response to the selection of another kind of connection.

5. In a telephone system, a selector, connectors and trunk lines selectable by said selector, means responsive to the selection of a connector by said selector for repeating subsequent impulses incoming to said selected connector over a certain conductor for the control thereof, and means responsive to the selection of a trunk line by said selector for repeating subsequent impulses incoming to said selector over the tip and ring conductors of the selected trunk in simplex.

6. In a telephone system, a selector, connectors and trunk lines selectable by said selector, a pulsing relay in said selector, means responsive to the operation of said pulsing relay by one series of impulses incoming to the selector for actuating it to select either a connector or trunk line, means responsive to the operation of said pulsing relay by a second series of impulses if a connector has been selected for transmitting a corresponding series of impulses over a certain conductor to said connector and if a trunk line has been selected for transmitting a corresponding series of impulses over a certain conductor to said connector and if a trunk line has been selected for transmitting a corresponding series of impulses over said selected trunk.

7. In a telephone system, a selector, connectors, trunk lines, means in said selector operative by one series of impulses received thereby for operating said selector to select either a connector or a trunk line, and means responsive to the reception or" a second series of impulses by said selector for repeating a corresponding series of impulses in a certain manner to a connector if selected and in a different manner to a trunk line if selected.

8. In a telephone system, a selector, connectors, groups of trunk lines, means in said selector operative by one series of impulses received by said selector for operating it to select either a connector or a group of trunks, means responsive to the selection of a group of trunks for operating said selector to hunt for and connect with an idle trunk in the selected group of trunks, and means thereafter responsive to series of impulses received by said selector for repeating corresponding series of impulses in one manner to a connector if selected or in another manner to a trunk if selected.

9. In a telephone system, a selector, connectors and trunk lines selectable by said selector, a control conductor, means for repeating impulses incoming to the selector over the talking leads in simplex to a selected trunk line and over said control conductor to a selected connector.

10. In a telephone system, a selector, connectors and trunk lines selectable by said selector, talking conductors and another conductor in said selector, means for repeating series of impulses incoming to said selector over said talking conductors in simplex operable if a trunk line is selected and for repeating series of impulses incoming to said selector over said other conductor if a connector is selected.

LEE R. WALLER. 

